These findings need to be validated, but they are interesting.  From a Medscape UK summary:

“In the first large study of its kind, tattoos were found to raise the risk for malignant lymphoma by about 20% compared with no tattoos. Tattoo ink often contains carcinogens and, when applied to the skin, triggers an immunologic response.

This study was a population-based case-control study of all incident cases of malignant lymphoma in Swedish adults (aged 20-60 years) in the Swedish National Cancer Register between 2007 and 2017 (n = 11,905). Tattoo exposure was assessed by a structured questionnaire in both cases and three random age- and sex-matched controls without lymphoma. The primary outcome was the incidence rate ratio of malignant lymphoma in tattooed vs nontattooed individuals.
The prevalence of tattoos was 21% among cases and 18% among controls. After adjustment for confounders, tattooed participants had a 21% higher risk for overall lymphoma than non-tattooed participants (incidence rate ratio = 1.21; 95% CI, 0.99-1.48).

And a link to the original paper, Tattoos as a risk factor for malignant lymphoma: a population-based case–control study, by Nielsen, Jerkeman, and Jöud. 

I guess I’m happy to be ink-free…